Temperature responsive timer control for a clothes drier



July 27, 1965 H. w. DEATON ETAL 3,

TEMPERATURE RESPONSIVE TIMER CONTROL FOR A CLOTHES DRIER Filed Sept. 19, 1960 3 Sheets-Sheet l INVENTORS F I g Homer w Deafon /iaymond M. Hutch/n50!) 77; air Ahorney y 7, 1965 H. w. DEATON ETAL 3,196,553

TEMPERATURE RESPONSIVE TIMER CONTROL FOR A CLOTHES DRIER Filed Sept. 19, 1960 5 Sheefis-Shet 2 98 Fig. 5

INVENTORS 4 Homer W. 0ea/0n By Raymond M. Hu/cbms on 7' lreir Affomey y 27, 1965 H. w. DEATON ETAL 3,196,553

TEMPERATURE RESPONSIVE TIMER CONTROL FOR A CLOTHES DRIER Filed Sept. 19, 1960 3 Sheets-Sheet 3 230 232 mmvroxs F, 7 Homer W Benton 9 BY Raymond M Hu/c/r/nson The/r Affarney United States Patent 3,1%,553 TEMPERATURE RESPUNSHVE TEMER CGNTRGL FUR A CLGTHES DRIER Homer W. Benton and Raymond M. Hutchinson, Dayton,

Uhio, assignors to General Motors (Iorporation, De-

troit, Mich, a corporation of Delaware Filed Sept. 19, 1960, er. No. 56,930 7 Ulaims. (Ql. 34-45) This invention relates to a domestic appliance and more particularly to an improved control arrangement for terminating a clothes drying cycle.

The clothes drying art has been faced with the disadvantage of venting the moisture laden exhaust products from a dryer to the outside atmosphere. For those situations where construction or other problems prevent outside venting, the condensing clothes dryer has been devised. Briefly, a condensing dryer of the type taught generally in the copending application Serial No. 723,573, filed May 2, 1958, now Patent No. 3,032,887, issued May 8, 1962, and assigned to the same assignee as this invention may include a recirculating drying air flow system for picking up moisture from the clothes and a cooling air flow system which blows in counter flow heat transfer relationship to the recirculating air. Thus, the recirculating air picks up moisture in the tumbling drum and, while passing through a heat exchanger, is cooled by the cooling air flow system, so that the entrained moisture will be released as condensate.

Certain conditions arise however in the use of a condensing dryer. Moisture droplets are deposited within the duct work of the recirculating dryer air system as the clothes are being dried. After the clothes are preferably dry, these moisture droplets start to evaporate and produce a decided cooling effect (dry bulb temperature of the recirculating air decreases). On the other hand, while the recirculating air is moisture laden, the cooling air is directed to absorbing the large latent heat load resulting from the heat of condensation. Again, as the clothes become properly dry, this latent load drops off, the heat of condensation is minimized, and the cooling air is effective to carry off the sensible heat. At this point, the dry bulb temperature of the cooling air decreases as did the temperature of the recirculating air. It is here proposed to sense either of these temperature drops with a thermostatic device which will maintain a closed circuit during rising or steady temperature conditions but which will break the circuit when a falling temperature condition occurs.

Accordingly, it is an object of this invention to provide means for sensing a falling temperature condition in a condensing dryer.

It is another object of this invention to provide a condensing dryer having a recirculating air flow system and a cooling air flow system with means in the outlet of said cooling air system for sensing a falling temperature to terminate a clothes drying cycle.

A more specific object of this invention is the provision of a thermostat for sensing the point at which tempreature starts to decrease.

Another object of this invention is the provision of a thermostat for sensing a falling temperature, wherein said thermostat includes a pair of bimetal levers, one of said bimetal levers operating in response to a rising temperature to maintain a circuit closed and the other of said bimetal levers operating upon a falling temperature to prevent the maintenance of said circuit closed.

Generally speaking, the object of this invention is the provision of a thermostat having a pair of bimetals, one of which bimetals permits the effective operation of the other of said bimetals in one direction only.

hi lifiii Patented July 27, 1965 Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a fragmentary perspective view of a condensing dryer with parts broken away to show the recirculating air flow system and the cooling air flow system;

FiGURE 2 is a top view elevational view of a thermotat suitable for use with the condensing dryer of FIGURE FIGURE 3 is a side elevational view of the thrmostat shown in FIGURE 2;

FEGURE 4 is an end elevational View taken along line 4 in FIGURE 2;

FIGURE 5 is a sectional view in FIGURE 3;

FIGURE 6 is an elevational view of another thremostat suitable for use with this invention; and

FIGURE 7 is a schematic wiring diagram of the falling temperature sensing dryer termination arrangement of this invention.

In accordance with this invention and with reference to FIGURE 1, a condensing type clothes dryer It) is illustrated. The clothes dryer It) is comprised of a casing having a top panel 12, a back panel 14 and side panels, such as 16. A control housing 18 is disposed on the top panel 12 and supports a knob 19 for initiating and controlling the drying cycle in accordance with the teachings of this invention. A tumbling drum 2% is disposed Within the casing and interposed between front bulkhead 22 and a rear bulkhead 24. The tumbling drum 2% is comprised of a rear wall 26 perforated at 27 which is rotatably supported on a stub shaft 28 journaled on the rear bulkhead 24. Further, the tumbling drum 2% includes an annular front Wall St terminating in a cylindrical access collar 32 which is relatively rotatably supported by a front port plate 34 carried on the bront bulkhead 22. The access opening formed by the collar 32 is closed by a door shown at 36. A lint collecting housing 38 is carried by the door 36 and projects into the access opening collar 32 of the tumbling drum when the door is closed, an annular seal 37 engaging the port plate shoulder 39 to force all air leaving the tumbling drum to travel through the lint collecting housing.

The recirculating air flow system is defined by perforations 4% in the front port plate 34 which open into a front duct 42. The front duct 42 has an opening 44 into an inlet header 46 for a heat exchanger or condenser shown generally at 48. The condenser 48 is comprised of a plurality slightly leftwardly sloping tubes 5i which interconnect the inlet header 46 with an outlet header 52. A recirculating air blower 54 has its inlet 5s connected to the outlet of the outlet header 52 and impels air through :a flexible conduit 58 to a rear duct 6% behind the rear bulkhead 24. A rear duct has an opening 62 through the rear bulkhead 24 into an annular chamber formed by a generally channel shaped annular pan 64 fastened to the front side of the bulkhead 24. The annular channel or heater housing provides the means for enclosing and supporting the annular heating elements 66 in juxtaposition of the perforated rear wall 26 of the tumbling drum.

Thus, recirculating drying air is impelled by the blower 54 through the flexible conduit 58 to the rear duct 6!). From the outlet opening 62 in the rear duct 60 air enters the heater chamber formed by the channel pan 64. The air is heated by the heating element 66 and enters the tumbling drum 20 through the perforations 27 in the taken along line 5-5 drum wall 26. Moisture is entrained from the clothes ano e-as in the tumbling drum and this moisture--ladene-d air flows out of the drum by way of the access opening collar 32 and the lint collecting housing 38 into the front duct 42 by way of the port plate openings 44 This air is channeled through the inlet header 46 for the condenser 4t; and through the tubes t) into the outlet header 52. While traveling through the condenser tubes 50, moisture is deposited therein by the cooling air flow system which will be described next following and this moisture flows by gravity into the outlet header 52 where an opening 7tl channels the moisture to a mating opening 72 in a removable substantially enclosed envelope-like condensate container 74. The inlet opening 72 in the condensate container 74 is the only opening in this completely enclosed container and thus the condensate container 74 may be slidably removed from the dryer and carried in vertical fashion to any suitable drain.

The cooling air system for the condenser 43 is comprised of a cooling air blower 76 connected by way of a fan-shaped duct 78 to the rear side of the condenser tubes 56. The blower 76 is effective to draw air through a screened opening St? at the front of the condenser tubes 50, over the outside of the condenser tubes 50 and int-o the duct '78, from which point the air is impelled to the atmosphere. This relatively cool air will cool the condenser tubes 50 and cause condensation of moisture from the recirculating air therein.

A single prime mover or motor 82 is effective through a belt and pulley system (not shown) behind the rear bulkhead 24 to rotate the tumbling drum 2t] and to drive the cooling air blower 76 and the recirculating air blower 54.

Note also that the condenser 48 is removable for periodic cleaning. A latch arm 84 (shown in the unlatched position) may be released to permit the entire condenser assembly of screen, tubes and end plates to be slidably removed from between the inlet header 46 and the outlet header 42. Water is simply run over and through the condenser tubes 5@ to remove any sediment which might accrue therein over extended usage.

The two air flow systems have been shown by arrows in FIGURE lthe solid arrows indicating the recirculating air flow and the dashed arrows indicating the cooling air flow for the condenser 4-8.

As aforesaid, the condensing dryer It is known to possess certain temperature drop characteristics which are indicative of clothes dryness within the tumbling drum 2d. It has been determined that these sudden temperature drops may be sensed to terminate the drying cycle when the clothes are at the proper end point dryness. In the recirculating air flow system slight moisture droplets are deposited during the time when the moisture is intense. As the clothes near their proper end point dryness, this moisture starts to evaporate and a sudden decrease in temperature is noted within the ducts 53 and 60. Similarly a decided drop in temperature is noted within the cooling air flow system in the duct 78. This latter is due to the fact that the cooling air is no longer carrying away the relatively large heat of condensation brought about by the action of the condenser on the recirculating air. It is, thus, the object of this invention to provide a thermostatic device, such as the thermostats 94} or 92 in either the cooling air flow duct 7% (solid line in FIGURE 1) or the rear duct 6t? (phantom line in FIGURE 1) to sense this sudden drop in sensible temperature as the means for terminating the drying cycle.

One falling temperature sensing thermostat 92 is shown in FIGURES 2, 3, 4 and 5. The thermostat 92, which may be installed in the same fashion as thermostat 9th, is comprised of a thermostat base 94 of insulating material, such as a 1 inch phenolic. The base 94 is ported at 96 for attachment within a dryer duct. A generally U-shaped bi-metal thermostat sensing arm 98 having a free end 99 and a fixed end M1 is fastened to the underside of the base 9 3 by rivets 100 and 1W2. The thermostat sensing arm 98 may be made of a .025 bimetal such as sold under the trade name More-flex and extends around the left end of the base 94 into overlying relationship with a contact button 104- forming a part of the rivet m2. An electrical connector spade 1% is fastened to the rivet 1M and the connected end of the bimetal 98 such that the spade 11%, the contact button 104, and the bimetal '98 are all electrically connected. Note that the bimetal 98 carries a contact button 1% which extends through the free end 99 of the bimetal arm to engage the fixed contact 1.64 on the thermostat base 94. With an increase in temperature the free end 99 of the sensing arm will move upwardly away from the base 94.

At the left end of the thermostat base 94 a pair of notches 110, 112 are formed to receive .a U-shaped bimetal thermostat holding clutch lllld. This clutch includes an upstanding leg or arm 116 and an upstanding leg or arm H8 interconnected by an integral base 129 fastened as'by a rivet 122 to the underside of the base 94. The thermostat holding clutch 114 may be formed of any suitable bimetal material such as a .020 More-flex bimetal. The object of the operation for the thermostat holding clutch 114 is for the upstanding arms 116 and 118 to move toward each other upon an increase in temperature. This object may be accomplished in bimetals in a variety of ways by utilizing different lengths, different materials and combinations of different materials and lengthsthe desideratum being merely to get the contact MP8 to back off or return as quickly as possible at the point where temperature starts to fall.

Between the upstanding arms 116 and 118 of the clutch 114 is a thermostat operating arm 126 of brass or other suitable material. The operating arm 126 includes a contact button 128 at one end thereof and at the other end thereof a pair of depending tabs or ears 139 and 132. Carried by the ears 1% and 132 is an operating arm pin 134 for pivotally supporting the operating arm 1%. The upstanding legs 116 and 118 of the thermostat holding clutch 114 include oversized holes 135 and 133 to permit the pin 1% to pivot freely in the upstanding legs of the bimetal clutch as well as permitting the legs 116 and 118 of the clutch to move laterally in relationship to the pin 1 .34.

The base 94- also carries another electrical connecting spade 14d which is connected by means of a Wire or electrical conductor 142 to the operating arm 126-the ter minal end 14-4 of the wire being Welded or otherwise suitabiy connected to the top of the operating arm 126.

With the foregoing construction it should now be seen that a switch has been provided between the electricai connecting spades res and 11.49, namely, the switch as defined by the contacts 1% and 128. The thermostat 92 will operate as follows. When the thermostat is disposed in an air stream such as in the position indicated by thermostat 9% in FIGURE 1, the air temperature will rise as the clothes drying cycle is initiated. As the temperature rises, the bimetal thermostat sensing arm 93 will open up with the contact 1% pushing the contact 128 ahead of it. At the same time, the rising air temperature will cause the upstanding legs or arms 116, 113 of the clutch 114 to move inwardly, thereby biasingly gripping the legs 13% and 132. of the thermostat operating arm 126. As aforesaid, the temperature in the duct will continue to rise so long as the clothes are drying with the sensing arm 98 and operating arm 126 assuming the phantom line positions of FIGURE 3. However, when the fabric has ceased to give up moisture, the heat of condensation within the condenser 48 will cease and the dry bulb temperature within the duct '78 will drop suddenly. The bimetal sensing arm 98 will sense this sudden drop in temperature and will tend to retract to the position shown in solid line in FIGURE 3. However, the rate of relaxation for the bimetal holding clutch lllld is slower than the bimetal sensing arm 98, therefore the holding clutch 1314 will retain the operating arm 126 in the phantom line position of FIGURE 3. Thus, with the contact 1% backing toward its normal posiareassa tion and the contact 128 in its phantom line position, the switch will be broken and the drying cycle terminated.

Turning now to the thermostat embodiment tl shown in FIGURE 6, the thermostat is shown comprised of an open boxlike support base or receptacle 160 having a back wall 165 from which extends upstanding walls 162, 164, and 166. Externally fastened to the wall 162 is an electrical spade connector 163 and to the receptacle wall 164 is an electrical spade connector 176. A bimetal thermostat sensing arm 172 is electrically connected to the spade 16S and to the support base wall 162 by a rivet 174. The sensing arm 172 carries a contact 176 on the free end thereof which is movable in accordance with the thermal fiexation of the bimetal 172. The back wall 165 of the support base 166 has pivotally supported thereon a ratchet wheel 178 which has a ratchet or serrated portion 180 along one section of the wheels periphery. The wheel 178 may be of nylon or other suitable electrically nonconducting material. Attached as at 181 to the wheel 178 is a metal thermostat operating arm 18?. having a contact 184 in normal engagement with the contact 176. Such normal engagement of the contacts 176 and 134 may be accomplished by mounting the casing back wall 165 vertically as shown or by spring loading the Wheel 178 in the counterclockwise direction. One end of the arm 182 is connected electrically through a pigtail 186 to the spade 170. Disposed upon the wall 166 of the support base 160 is a second bimetal holding clutch arm 1% which has a pawl portion 192 in juxtaposition to the teeth or serrations 1811 of the ratchet wheel 178.

During a rise in temperature, the bimetal sensing arm 172 moves in a clockwise direction, as does the bimetal pawl arm 190. The action of the sensing arm biases the operating arm 182 and thereby rotates the ratchet wheel 1'78 clockwise. At the same time the pawl portion 192 of the clutch 190 is engaged with the ratchet wheel to permit clockwise rotation only. Upon a decrease in temperature,

the bimetal 172 will return to its normal relaxed position more quickly than the bimetal 1M But the relatively slow relaxation of the clutch arm 191) keeps the pawl in the ratchet wheel for retaining the contact 154 at the highest level reached during temperature rise due to the bias of the bimetal 172. When the contact 176 falls away from the contact 184, the switch will open to interrupt a circuit.

The novel dryer termination cycle of this invention will now be described with reference to FIGURE 7 wherein the thermostat 20 has been used by way of example only. It should be recognized that the thermostat 92 will work equally Well in the circuit and that either thermostat 99 or 92 may be placed in either the cooling air duct 78 or the rear duct 61). To control the dryer in accordance with the concepts of this invention a timer 200 is provided having an intermittently rotatable timer shaft 2E2, a heater cam 204, a timer motor cam 206, a prime mover and interior lamp cam 2118 and a timer motor 211) for rotating the timer shaft 202. A power source L L and a neutral (N) provide a 230-volt source of power for the dryer. The timer heater cam 2114 operates a timer switch 212 on a timer contact to selectively condition the drying heater 66 for operation. In the heater circuit a motor speed switch 214 is included and adapted to be closed when the motor 82 is running. This is a safety means to insure that the motor is operating and thus the tumbling drum rotating before the heater 66 can be energized.

The timer motor 210 is controlled by the timer motor switch 216 operating on a contact 218. In parallel with the timer motor 216 is the thermostat 9t) which has its movable switch contacts 176 and 184 in series electrical flow relationship with a coil 220 for operating a relay switch 222 in series with the timer motor 216 and the timer switch 216.

The primary motor 82 is energized through a timer switch 224 actuated by the cam 208 and a timer contact 226. A door switch 228 is positioned between the timer switch 224 and the motor 82 and movable between a door opened contact 230 when dryer door 36 is open and a door closed contact 232 when the dryer door is closed.

As a safety feature, the circuit includes a means for bypassing the control system and running out the time cycle in those cases where the load to be dried has retained such a small amount of moisture that no significant drop in temperature occurs for the thermostat to sense. This safety action is accomplished by a limiter thermostat 236 in the front duct of the dryer 1!). This safety device includes a switch blade 238 which operates between a heater contact 240 and a heater by-pass contact 242 in series With the timer motor 210. Thus, a small load of say one pound or less might be placed in the dryer 1t) and the cycle initiated. If the amount of moisture given up is insignificant, the temperature in the ducts 76 and 61) will continue to rise without a noticeable decrease. When the temperature passes a predetermined level above the highest temperature normally sensed by the thermostat 91), the switch blade 238 will move to the contact 242 and the timer motor 210 will be continuously energized until the entire cycle is run out.

In operation one will place a quantity of damp fabric within the tumbling drum 20 and close the door 36, thereby positioning the door switch blade 229 on the door closed contact 232. The timer starting knob or actuator 19 will be turned manually, thereby rotating the cam shaft 202 to close the timer switches 212, 216 and 224. The tumbling drum 20 and the blowers 54- and 76 will be operated when the motor 32 is energized from L through line 24a, timer switch blade 224, timer contact 226, line 248, the door switch blade 22?, the door closed contact 232 and motor 82 to the neutral (N) side of the line. Thus, both the recirculating drying air fiow system and the cooling air flow system are initiated.

Substantially simultaneous with the operation of the air flow systems and the motor 82, the heater 66 will be energized on 230 volts from L through timer switch blade 212, timer heater contact 213, the limiter thermostat switch blade 233, thermostat contact 240, the heater 66 and the motor speed switch 214 to L Also substantially simultaneous with the operation of the heater 66 and the motor 82 is the operation of the timer motor 210 when the timer switch 216 is closed on the timer contact 218. However, instantaneously, the timer motor 210 is deenergized as the coil 226 of the relay switch 222 is energized as follows: from L line 246, timer switch blade 216, timer contact 218, line 250, the bimetal sensing arm 172, contacts 176 and 184, the operating arm 182, the terminal connector 170, the coil 220 to the neutral (N) side of the line. The energization of the coil 220 will lift the switch blade 222 and open the circuit to the timer motor 210, thereby deenergizlng the timer motor throughout the clothes drying portion of the cycle.

Moisture laden air will be carried through the condenser 48 where it will deposit the moisture in the form of condensate. As the cooling air picks up this heat of condensation, the temperature within the cooling air duct 78 will continue to rise. Since the thermostat 90 is disposed in the duct 78, the bimetals 172 and 190 will flex in accordance with the increase in temperature. More particularly, the clutch pawl 190 will move into engagement with the teeth of the ratchet wheel 178. Simultaneously, the bimetal 172 will bias the operating arm 182 upwardly throughout the temperature increase within the duct 78. After the highest temperature is reached (indicated by the operating arm 182 in phantom line in FIGURE 6), the bimetal 172 will quickly start to respond to the dropping temperature within the duct 78. The bimetal 172 will return to its normal position more quickly than will the slower acting bimetal 1%, which remains engaged with the teeth of the ratchet wheel 178. Thus, bimetal retains or immobilizes the operating arm 182 in its highest phantom line position. As the contact 176 quickly backs away from the contact 184-, the circuit to the relay coil 22% is broken and the relay switch 222 will close thereby energizing the timer motor 23th to run out the cycle.

As the timer motor v210 returns to operation, it will next open the timer switch blade 212 to .deenergize the heater 66. This will initiate a cool-off period during which the fabric temperature is lowered to a condition more suitable for handling. After an interval of approximately ten minutes, the timer switch blades 216 and 224 will be opened to terminate the drying cycle.

In brief, the timer operates in three steps. First, the timer switches 212, are and 224 are closed. Second, timer switch 212 opens while the switches 216 and remain closed. Lastly, the switches 2.16 and 224 are opened to terminate the cycle.

It should now be seen that an improved drying cycle has been provided including a thermostat which senses a drop in temperature in a dryer and uses such drop to break a circuit and terminate the drying cycle. The specific thermostats of this invention are simple in construction and dependable in operation More generally, the thermostats of this invention provide a means for using a pair of bimetals to sense a temperature drop, one being effective during a risin temperature and the other being effective during a falling temperature.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A control circuit for a condensing dryer having means defining a recirculating air stream and a single pass cooling air stream in heat transfer relationship to said recirculating air stream, a heater for said recirculating air stream and a primary motor for initiating said air streams comprising means for sequentially controlling said heater and said primary motor in a drying cycle including a timer motor and a timer switch, a thermostat in the outlet of said cooling air stream having a thermostat switch rand a thermally responsive means for controlling said thermostat switch, a relay switch in series with said timer motor and said timer switch and having a relay coil for actuating said relay switch in series with said thermostat switch and said timer switch and in parallel with said timer motor and said relay switch, said relay coil adapted to open said relay switch when said coil is energized and adapted to close said relay switch when said coil is deener-gized, said thermostat switch having a pair of movable contacts in series with said relay coil and being normally closed upon increase in temperature to condition said relay coil for energization, and said thermally responsive means operating to restrain one of said contacts, thereby to open said thermostat switch to deenergize said relay coil and start said timer motor to terminate said drying cycle upon a decrease in said temperature.

2. A control circuit for a condensing dryer having means defining a recirculating air stream and a cooling air stream in heat transter relationship to said recirculating air stream, a heater for said recirculating air stream and a primary motor for initiating said air streams comprising means for sequentially controlling said heater and said primary motor in a drying cycle including a timer motor and a timer switch, a thermostat in said recirculating air stream upstream from said heater and having a thermostat switch and a thermally responsive means for controlling said thermostat switch, a relay switch in series with said timer motor and said timer switch and having a relay coil for actuating said relay switch in series with said thermostat switch and said timer switch and in parallel with said timer motor and said relay switch, said relay coil adapted to open said relay switch when said coil is energized and adapted to close said relay switch when said coil is deenergized, said thermostat switch having a pair of movable contacts in series with said relay coil and being normally closed upon increase in temperature to condition said relay coil for energization, and said thermally responsive means operating to restrain one of said contacts, thereby to open said thermostat switch to deenergize said relay coil and start said timer motor to terminate said drying cycle upon a decrease in said temperature.

3. In combination with a condensing dryer having condensing means defining a recirculating air stream and a cooling air stream in heat transfer relationship to said recirculating air stream, heating means for said recirculating air stream and blower means for initiating said air streams, a control circuit comprising means for sequentially controlling said heating means and said blower means in a drying cycle including a timer motor, a thermostat in said cooling air stream downstream from said condensing means and having a thermally responsive thermostat switch means responsive only to the temperature of said air stream downstream from said condensing means for energizing and deenergizing said timer motor and a thermally responsive holding means responsive only to the temperature of said air stream downstream from said condensing means for controlling said thermostat switch means, said thermostat switch means being normally closed upon increase in temperature to 'deenergize said timer motor, and said thermally responsive holding means being effective to open said thermostat switch means to energize said timer motor substantially immediately upon a decrease in said temperature.

4. In combination with a condensing dryer having condensing means defining a recirculating air stream and a cooling air stream in heat transfer relationship to said recirculating air stream, heating means for said recirculating air stream and blower means for initiating said air streams, a control circuit comprising means for sequentially controlling said heating means and said blower means in a drying cycle including a timer motor, a thermostat in one of said air streams downstream from said condensing means and having a thermally responsive thermostat switch means responsive only to the temperature of said air stream downstream from said condensing means for energizing and deenergizing said timer motor and a thermally responsive holding means responsive only to the temperature of said air stream downstream from said condensing means for controlling said thermostat switch means, said thermostat switch means being normally closed upon increase in temperature to maintain said timer motor deenergized, and said thermally responsive hol ing means being effective to open said thermostat switch means to energize said timer motor substantially immediately upon a decrease in said temperature.

5. In combination with a condensing dryer for moist fabric having means for agitating said fabric, condensing means, means defining a recirculating air flow including said agitating means and said condensing means, means defining a cooling air flow in heat transfer relationship to said recirculating air flow in said condensing means for condensing moisture from said recirculating air flow and means for inducing said air flows, drying cycle control means having a timer means for starting and automatically stopping said agitating means and said inducing means, said control means including a temperature responsive device in one of said air flows downstream from said condensing means, said temperature responsive device having contacts in power supply control relationship to said timing means and solely responsive to the temperature of said air flow downstream from said condensing means, said contacts quickly actuatable in response to av decrease in temperature of said air flow downstream from said condensing means, thereby to initiate the termination of said drying cycle.

6. A control circuit for a condensing dryer having means defining a recirculating air stream and a cooling air stream in heat transfer relationship to said recirculating air stream, a heater for said recirculating air stream and primary motor means for initiating said air streams comprising means for sequentially controlling said heater and said primary motor means in a drying cycle including a timer motor and a timer switch, a thermostat in said recirculating air stream upstream from said heater and having a thermostat switch and a thermally responsive means for controlling said thermostat switch, a timer motor switch in series with said timer motor and said timer switch and having means in controlled relationship to said thermostat switch for actuating said timer motor switch, said controlled means adapted to open said timer motor switch when said controlled means is energized and adapted to close said timer motor switch when said controlled means is deenergized, said thermostat switch having a pair of movable contacts in series with controlled means and being normally closed upon increase in temperature to condition said controlled means for energization, and said thermally responsive means operating to restrain one of said contacts, thereby to open said thermostat switch to deenergize said controlled means and start said timer motor to terminate said drying cycle upon a decrease in said temperature.

'7. A control circuit for a condensing dryer having means defining a recirculating air stream and a cooling air stream in heat transfer relationship to said recirculating air stream, a heater for said recirculating air stream and primary motor means for initiating said air streams comprising means for sequentially controlling said heater and said primary motor means in a drying cycle including a timer motor and a timer switch, a thermostat in the outlet of said cooling air stream having a thermostat switch and a thermally responsive means for controlling said thermostat switch, a timer motor switch in series with said timer motor and said timer switch and having means in controlled relationship to said thermostat switch for actuating said timer motor switch, said controlled means adapted to open said timer motor switch when said controlled means is energized and adapted to close said timer motor switch when said controlled means is deenergized, said thermostat switch having a pair of movable contacts in series with said controlled means and being normally closed'upon increase in temperature to condition said controlled means for energization, and said thermally responsive means operating to restrain one of said contacts, thereby to open said thermostat switch to deenergize said controlled means and start said timer motor to terminate said drying cycle upon a decrease in said temperature.

References Cited by the Examiner UNITED STATES PATENTS 1,839,935 1/32 Thomas 200-1385 2,678,379 5/54 Fry 200-1385 2,743,533 5/56 Smith 34-75 2,830,157 4/58 Patti 200-1385 2,875,526 3/59 Engel 34-45 2,378,580 3/59 Hughes 34-45 2,882,610 4/59 Hughes 34-45 2,895,230 7/59 Reiley 34-45 2,903,799 9/59 Sachaczenski 34-45 2,904,895 9/59 Bochan 34-4-5 2,991,342 7/61 Weber 34-45 3,022,987 2/62 Thorsheim 34-45 3,028,680 4/62 Conlee 34-45 FOREIGN PATENTS 225,397 4/59 Australia.

NGRMAN YUDKOFF, Primary Examiner. BENJAMIN BENDETT, Examiner. 

1. A CONTROL CIRCUIT FOR A CONDENSING DRYER HAVING MEANS DEFINING A RECIRCULATING AIR STREAM AND A SINGLE PASS COOLING AIR STREAM IN HEAT TRANSFER RELATIONSHIP TO SAID RECIRCULATING AIR STREAM, A HEATER FOR SAID RECIRCULATING AIR STREAM AND A PRIMARY MOTOR FOR INITIATING SAID AIR STREAM COMPRISING MEANS FOR SEQUENTIALLY CONTROLLING SAID HEATER AND SAID PRIMARY MOTOR IN A DRYING CYCLE INCLUDING A TIMER MOTOR AND A TIMER SWITCH, A THERMOSTAT IN THE OUTLET OF SAID COOLING AIR STREAM HAVING A THERMOSTAT SWITCH AND A THERMALLY RESPONSIVE MEANS FOR CONTROLLING SAID TIMER MOTOR SWITCH, A RELAY SWITCH IN SERIES WITH SAID TIMER MOTOR AND SAID TIMER SWITCH AND HAVING A RELAY COIL FOR ACTUATING SAID RELAY SWITCH IN SERIES WITH SAID THERMOSTAT SWITCH AND SAID TIMER SWITCH IN PARALLEL WITH SAID TIMER MOTOR AND SAID RELAY SWITCH, SAID RELAY COIL ADAPTED TO OPEN SAID RELAY SWITCH WHEN SAID COIL IS ENERGIZING AND ADAPTED TO CLOSE SAID RELAY SWITCH WHEN SAID COIL IS DEENERGIZED, SAID THERMOSTAT SWITCH HAVING A PAIR OF MOVABLE CONTACTS IN SERIES WITH SAID RELAY COIL AND BEING NORMALLY CLOSED UPON INCREASE IN TEMPREATURE TO CONDITION SAID RELAY COIL FOR ENERGIZATION, AND SAID THERMALLY RESPONSIVE MEANS OPERATING TO RESTRAIN ONE OF SAID CONTACTS, THEREBY TO OPEN SAID THEREMOST SWITCH TO DEENERGIZE SAID RELAY COIL AND START SAID TIMER MOTOR TO TERMINATE SAID DRYING CYCLE UPON A DECREASE IN SAID TEMPERATURE. 